This invention relates to Austenitic Stainless Steel.
Traditionally, 300 series Austenitic Stainless Steels such as UNS S30403 (304L) and UNS S30453 (304LN) have specified chemical compositions in percentage by weight as illustrated in Table 1 herein:
TABLE 1UNS NoTypeCMnPSSiCrNiMoNS 30403304LMIN17.508.00MAX0.0302.000.0450.0300.7519.5012.00. . .0.10S 30453304LNMIN18.008.000.10MAX0.0302.000.0450.0300.7520.0012.00. . .0.16
There are a number of shortcomings with the abovementioned conventional Austenitic Stainless Steels associated with their particular specification ranges. This can potentially lead to a lack of proper control of the chemical analysis at the melting stage, which is necessary to optimise the properties of the Alloys to give an excellent combination of mechanical strength properties and good corrosion resistance.
The mechanical properties that are achieved, with Alloys such as UNS S30403 and UNS S30453 are not optimised and are relatively low compared to other generic stainless steel groups such as 22Cr Duplex Stainless Steels and 25Cr Duplex and 25Cr Super Duplex Stainless Steels. This is demonstrated in Table 2 which compares the properties of these conventional Austenitic Stainless Steels with typical grades of 22Cr Duplex, 25Cr Duplex and 25Cr Super Duplex Stainless Steels.
TABLE 2Mechanical Properties of Austenitic Stainless SteelsTensileYieldHardnessStrengthStrengthElongationNote 2MinMin2 in or 50 mmMaxUNS NoTypeKsiMPaKsiMPaMin %BrinellRockwell BS30403304L70485251704020192S30453304LN75515302054021795TensileYieldHardnessStrengthStrengthElongationNote 2MinMin2 in or 50 mmMaxUNS NoTypeKsiMPaKsiMPaMin %BrinellRockwell CMechanical Properties of 22Cr Duplex Stainless SteelsS31803220590620654502529331S32205220595655654502529331S32304230487600584002529032Mechanical Properties of 25Cr Duplex and 25Cr Super Duplex Stainless SteelsS32760. . .1087508055025270. . .S327502507116795805501531032S39274. . .116800805501531032S32520. . .1127708055025310. . .Note 2The hardness figures quoted apply to the solution annealed condition.
It is an object of the present invention to provide an austenitic stainless steel which alleviates at least one of the disadvantages of the prior art and/or provide the public with a useful choice.